Abstract
BackgroundBreathlessness is associated with major adverse health outcomes and is twice as common in women as men in the general population. We evaluated whether this is related to their lower absolute lung volumes.MethodsCross-sectional analysis of the population-based Swedish CardioPulmonarybioImage Study (SCAPIS) Pilot, including static spirometry and diffusing capacity (n = 1,013; 49% women). Breathlessness was measured using the modified Medical Research Council (mMRC) scale and analyzed using ordinal logistic regression adjusting for age, pack-years of smoking, body mass index, chronic airway limitation, asthma, chronic bronchitis, depression and anxiety in all models.ResultsBreathlessness was twice as common in women as in men; adjusted odds ratio (OR) 2.20 (95% confidence interval, 1.32−3.66). Lower absolute lung volumes were associated with increased breathlessness prevalence in both men and women. The sex difference in breathlessness was unchanged when adjusting for lung function in %predicted, but disappeared when controlling for absolute values of total lung capacity (OR 1.12; 0.59−2.15), inspiratory capacity (OR 1.26; 0.68−2.35), forced vital capacity (OR 0.84; 0.42−1.66), forced expiratory volume in one second (OR 0.70; 0.36−1.35) or lung diffusing capacity (OR 1.07; 0.58−1.97).ConclusionIn the general population, the markedly higher prevalence of breathlessness in women is related to their smaller absolute lung volumes.
Highlights
IntroductionBreathlessness is the cardinal symptom of cardiorespiratory disease and is strongly associated with adverse health outcomes.[1, 2] Activity-related breathlessness, measured as a modified Medical Research Council (mMRC) score ! 1, is reported by about 25 percent of the general adult population.[3,4,5] Breathlessness is about twice as common among women than men in the general population, and the reasons are unknown.[3,4,5] Age, educational level, smoking habits, body mass index (BMI), the presence of comorbidity, and lung function impairment measured as forced expiratory volume in one second (FEV1) or forced vital capacity (FVC) in percent of the predicted normal are all associated with the prevalence of breathlessness, but neither of these variables explain the sex difference.[3, 6, 7]Prevailing but unproven hypotheses are that the disparity in breathlessness between men and women is explained by differences in anxiety or depression, sociocultural differences in symptom report, hormonal changes related to menopause, or that women have smaller airways than men matched for lung size (dysanapsis).[8, 9]Recent mechanistic studies report that women have a lower maximal ventilatory capacity and use a greater fraction of their ventilatory capacity during exertion
The sex difference in breathlessness was unchanged when adjusting for lung function in %predicted, but disappeared when controlling for absolute values of total lung capacity, inspiratory capacity, forced vital capacity, forced expiratory volume in one second or lung diffusing capacity
Educational level, smoking habits, body mass index (BMI), the presence of comorbidity, and lung function impairment measured as forced expiratory volume in one second (FEV1) or forced vital capacity (FVC) in percent of the predicted normal are all associated with the prevalence of breathlessness, but neither of these variables explain the sex difference.[3, 6, 7]
Summary
Breathlessness is the cardinal symptom of cardiorespiratory disease and is strongly associated with adverse health outcomes.[1, 2] Activity-related breathlessness, measured as a modified Medical Research Council (mMRC) score ! 1, is reported by about 25 percent of the general adult population.[3,4,5] Breathlessness is about twice as common among women than men in the general population, and the reasons are unknown.[3,4,5] Age, educational level, smoking habits, body mass index (BMI), the presence of comorbidity, and lung function impairment measured as forced expiratory volume in one second (FEV1) or forced vital capacity (FVC) in percent of the predicted normal are all associated with the prevalence of breathlessness, but neither of these variables explain the sex difference.[3, 6, 7]Prevailing but unproven hypotheses are that the disparity in breathlessness between men and women is explained by differences in anxiety or depression, sociocultural differences in symptom report, hormonal changes related to menopause, or that women have smaller airways than men matched for lung size (dysanapsis).[8, 9]Recent mechanistic studies report that women have a lower maximal ventilatory capacity and use a greater fraction of their ventilatory capacity during exertion. For the same level of work or ventilation, women have increased work of breathing, neural respiratory drive, and exertional breathlessness compared with men.[6, 8, 10,11,12,13,14] The sex difference in breathlessness was attenuated when accounting for differences in absolute ventilatory capacity both in healthy and people with chronic obstructive pulmonary disease (COPD) during standardized exercise in the laboratory,[6, 8, 10,11,12,13] and in patients with severe COPD evaluated for lung volume reduction surgery.[15]. Breathlessness is associated with major adverse health outcomes and is twice as common in women as men in the general population We evaluated whether this is related to their lower absolute lung volumes
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